This! Maxi is too freaked out about war right now to think clearly. She’s so smart but couldn’t even pick up on the fact that her sister told her indirectly that their father now has a speech impediment. He mocked Maxi her whole life only to become that which he scorned as idiocy. (︶︿︶)=凸
The duke kept the sisters separate on purpose and abused them in such different ways that Maxi thought Rosetta lived a perfect life with no hardship. Rosetta was drowning in her own way and will finally escape with her loveless marriage to the prince. Rosetta became cold survive. My head-canon is that they exchange letters after the book’s story ends.

Everyone hates sister but she clearly cares her sister from distant. She uses that 'repay' to stop the war, not because she actually doesnt care Maxi. Thats strategic move from her side for everyones sake. And she is warning Maxi for her to be careful. Its not a threat. She just has brain to use situation. She is at fault for ignoring her father's abuse towards her sister but again, for long-termed how she could do? She waited to get more power so she could do something without getting harmed. She is very clever, also strategic character. Very realistic too, like a politician. I like her how she secretly cares for her sister, unlike typical scenario. I hope her and Maxi gets closer.